1. Field of the Invention
The present invention relates to an optical sheet and a backlight unit including the same, and more particularly, to an optical sheet for a display device and a backlight unit including the same.
2. Discussion of Related Art
Nano light-emitting bodies including quantum dots, which are materials having a crystal structure of several to several tens of nanometers in size, comprise several hundred to several thousand atoms. Even when nano light-emitting bodies are formed with the same materials, the band gaps increase as the sizes of the nano light-emitting bodies decrease, and thus the luminous characteristics thereof are changed according to the sizes. Further, even when the sizes of nano light-emitting bodies are the same, the luminous characteristics thereof are changed according to the materials which form the nano light-emitting bodies. These characteristics of nano light-emitting bodies are adjusted to use the nano light-emitting bodies in various light-emitting devices and electronic devices.
However, since the nano light-emitting bodies are very vulnerable to ultraviolet light, heat, moisture, and the like, there is a problem in that a lifetime of an electronic device is reduced when the nano light-emitting bodies are applied to the electronic device. Specifically, in a film or sheet including a nano light-emitting body, various methods in which the nano light-emitting body is protected from ultraviolet light, heat, moisture, or the like are being proposed. However, there is a limit to fundamentally preventing the moisture from penetrating into the film or the sheet.
Meanwhile, in general, a display device uses a white light source which emits white light. The white light passes through the color filters, and thus a user observing the display device may see color images. White light sources include blue light-emitting diode (LED) chips which emit blue light and a light switch so that the light source finally emits the white light using the blue light. Yttrium aluminum garnet (YAG), which is a fluorescent body, is mainly used as the light switch. However, since the fluorescent body has an emission spectrum in a range of the red light wavelength band and the green light wavelength band, there is a limit to increasing the color purity shown by light generated from the white light source using the fluorescent body which passes through the color filter. Further, the display devices using the white light source to which the fluorescent bodies are applied have low color reproducibility.
In order to improve the color reproducibility of display devices, various studies for applying nano light-emitting bodies having an emission spectrum in which a full width at half maximum (FWHM) is small and power density is high to display devices have been under way recently.